Effect of dexamethasone as an analgesic adjuvant to multimodal pain treatment after total knee arthroplasty: randomised clinical trial

Dear Editor

We read with great interest the paper entitled ‘Effect of dexamethasone as an analgesic adjuvant to multimodal pain treatment after total knee arthroplasty: randomised clinical trial’ by Kasper and colleagues published online on 11 January 2022 in British Medical Journal.[1] In a randomized clinical trial, the authors determined the effect of dexamethasone on morphine consumption and postoperative pain control after primary knee arthroplasty. The conclusion of their study is that ‘Two doses of dexamethasone reduced morphine consumption during 48 hours after total knee arthroplasty and reduced postoperative pain.’ At present, the use of multimodal analgesics is emphasized to enhance the early recovery of many orthopaedic patients. This well-designed study and conclusions of the author obviously contribute to the development of perioperative related clinical problems. Although we have read this article happily, it must be pointed out that this article raises some thought-provoking questions. Therefore, there are still several questions that we would like to communicate with the authors.

According to this study, ‘The first dose of the trial drugs was administered after onset of spinal or general anaesthesia, and the second dose 24 hours after the end of surgery.’ It is not clear that the specific time period of 24-hour administration after operation, and the metabolism of narcotic drugs will also be different. At the same time, the use of some narcotic drugs may lead to the analgesic effect of postoperative opioids.[2] How to control the bias in this process and whether it has a certain impact on the clinical results.

In the method section, the authors pointed out that ‘Secondary outcomes were levels of pain intensity measured using a visual analogue scale at 24 and 48 hours (score range: 0 mm (no pain) to 100 mm (worst pain imaginable)) during 45° flexion of the knee, at rest, and the highest level of pain experienced during the past 24 hours.’ However, it is not clear who collected data on VAS scores. Pain scores obtained by clinical nurses have been shown to be biased against analgesic studies, which may lead to other deviations in the results of the study. It is unclear whether the VAS scores at these points were repeatedly measured by 2 independent evaluators. Some studies have pointed out that when using vas to measure pain, frequent vas measurement and calculation of the area under the curve can better show the severity of pain than a small number of measurements.[3]

Last but not least, it is not clear in the study of Kasper et al whether the corresponding physical therapy is used (eg, the time and frequency of ice compress, the adjustment of the position of the affected limb, and the level of assistance required to complete each task). Meanwhile, the detailed information provided by statistical analysis can not fully determine whether appropriate statistical methods are used for the observed data. For example, what data is converted to meet the assumptions of ANOVA? VAS score or morphine consumption or both? How did they transform?

We hope that more orthopedic doctors will be interested in the perioperative analgesia mode of TKA, so as to promote the early recovery of patients. At the same time, we also respect the author's great contribution and are very interested in the author's response to the above questions.

Reference
1.Kasper G, Daniel H, Troels L, et, al, Effect of dexamethasone as an analgesic adjuvant to multimodal pain treatment after total knee arthroplasty: randomised clinical trial. BMJ 2022;376:e067325. doi: 10.1136/bmj-2021-067325.
2.Albrecht E, Grape S, Frauenknecht J, Kilchoer L, Kirkham KR. Lowversus high-dose intraoperative opioids: A systematic review with meta-analyses and trial sequential analyses. Acta Anaesthesiol Scand 2020;64:6-22. doi:10.1111/aas.13470
3. Dysart S, Snyder MA, Mont MA. A randomized, multicenter, double-blind study of local infifiltration analgesia with liposomal bupivacaine for postsurgical pain following total knee arthroplasty: rationale and design of the Pillar trial. Surg Technol Int 2016;30:261e7.